This PSU has an external, two pin Molex connector that provides
power to the case fan. There is a 9.25"Wx1.75"H inch hinged cover on the
lower outer side of the psu. It is fastened at the front by a single captive
standard screw. The cover pivots open on the rear hinges, revealing a three
pin Molex power connector, like a female drive power connector. The battery
cavity is 1.875" deep.

8550/Z PSURich keeps me honest
The original one coming with Mod 50.50z was rated 94 watts,
no fan. HMM says part number is [90x9366]. (Ed.
He's right, I remember the fan assembly that slides in at the back of the
case. Old age, I guess...)

This is from a 50Z. No side blower. (The blower
plugs into the motherboard, is supported by two plastic snaps to top rack,
and it blows out the rear of the 50/50z unit). CASE BOTTOM of power supply
does not have a screen, it has finely punched holes, 11 or 10 holes across,
the length of power supply.
Cases vary color, gold/silver. Security
torx, 5 on side 2 on top. Like unto Mod 70 supplys, except no side blower,
and lower rating.

Remove the Power Supply Remove the two screws at the back of the case. Remove
the screw at the front inner corner. Pull PS out from planar.

Power Supply Health The way these were built, they have a screen across the
bottom side. Just like on a clothes dryer, you have to remove "lint" from
the screen. I used a T-10 security Torx to open it.The fan is a Panaflow
DC Brushless, Model FBH-09A12L, 12v 0.14A or a Nidec Beta SL Model D09B-12PLL
12v .09A

JN1 Floppy 1 (A:)
JN2 Floppy 2 (B:)
The three resistor/capacitor pairs on the riser are for
DC-buffering and decoupling. The earlier risers lacked them and once you'd
stuffed in 2 FDDs or 1 FDD and a tape problems occured with loss of data
during copying and suchlike.

Please note that clone PC power cables use yellow/black/red,
while IBM systems use yellow/black, or red/black/blue. What is important
is the position of the conductor. Note that the drive power connector is
keyed with bevelled edges.

From Peter Wendt Warnings and recommendations:
The maximum power from this hack is about 5v/1A
and 12v/1A so if you have both disk-drives or one disk-drive and a tape-streamer
installed ... it is probably not a good idea anyway. It will -non
the less- work in most cases, until the unit driven over this port doesn't
take too much power. Most modern Harddisks will not exceed these limits.
In case of doubt: consult drive manual for its power-consumption.
Or don't do the modification.
If you have only one disk-drive installed, take
the connector of the second drive for modification. Caution!! Take
care not to damage the tiny connections on the board near the connector
for Drive 2 while soldering the wires.
Remember, that the Mod. 50 / Mod. 70 power-supplies aren't that
powerful at all. Especially the Mod. 50 power-supply (94W!!!) is known
to have lesser power than assumed. If you'd already installed a -386/-486
upgrade, 64Megs of RAM, SCSI-adapter and a Hi-Resolution graphic board
it will surely collapse.